Thanks to its proximity to Athens, this island in the Argo-Saronic Gulf has become a popular weekend destination for locals and a worthwhile last stop for those visiting the city. Hydra’s elegant stone mansions are all constructed on the steep slopes around the main port—and thanks to a rule that bans new construction as well as motor vehicles, the island is an appealing time warp. Settle into a top-tier rental home from White Key Villas before exploring Hydra’s secluded beaches and discovering deliciously slow family-owned cafés and boutiques stocked with local treasures—all by foot, boat, or donkey.